Four-component microscope objective

ABSTRACT

A four-member microscope objective having a numerical aperture of 0.25 provides a magnification of substantially 10× and a substantially flat image field of 24mm in combination with a telescope objective as described in U.S. Pat. No. 3,355,234 and a typical 10× eyepiece.

BACKGROUND OF THE INVENTION

The present invention relates to microscope objectives, and moreparticularly, to an achromatic microscope objective with a numericalaperture of substantially 0.25 having four components. It is an objectof this invention to provide such a microscope objective which iswell-corrected for the usual chromatic image aberrations as well asspherical aberration, coma and astigmatism, while providing asubstantially flat image field of 24mm and a 10X magnification incombination with a telescope objective as described in U.S. Pat. No.3,355,234 and a typical 10X eyepiece.

The closest known prior art is U.S. Pat. No. 3,041,934 issued July 3,1962 to Rubin et al. This patent discloses a flat field objective havingfive elements. The principal distinguishing differences of the objectiveof the present invention and reference resides in the reversed positionof the second and third elements; the absence of a doublet in the priorart objective and the prior art objective does not provide parallellight exiting the last member of the objective.

THE DRAWING AND THE INVENTION

The drawing is an optical diagram of an objective X having lens elementsI, II, III and IV in alignment along an optical axis extending fromobject plane O.

The first element I is a biconcave negative singlet; the second elementII is a positive meniscus singlet; followed by lens element III which isa biconvex positive doublet. The parameters of objective X are set forthin Table I wherein the axial thicknesses of successive lens elements aredesignated T₁ to T₅, and the successive axial spaces from the objectplane O are designated S₁ to S₄. Successive lens radii are designated R₁to R₉ where the minus sign (-) applies to surfaces whose center ofcurvature lies on the object side of their vertices. The refractiveindices and Abbe number of the glasses in the successive lenses areabsolute values and designated ND₁ to ND₅ and √ 1 to √ 5, respectively.

                                      TABLE I                                     __________________________________________________________________________                               Index of Abbe                                      Lens                                                                             Radius (R)                                                                              Thickness (T)                                                                        Spacing (S)                                                                          Refraction (ND)                                                                        No. (√)                            __________________________________________________________________________                        S.sub.1  = .27032B                                           R.sub.1  =-  .28454B                                                       I            T.sub.1  = .08208B                                                                          1.53<ND.sub.1 <1.55                                                                    √.sub.1  ≅ 47               R.sub.2  =  3.91004B                                                                           S.sub.2  = .08876B                                           R.sub.3  =- 3.23135B                                                       II           T.sub.2  = .13680B                                                                          1.65<ND.sub.2 <1.67                                                                    √.sub.2  ≅ 50               R.sub.4  =-  .46730B                                                                           S.sub.3  = .14752B                                           R.sub.5  =  2.37855B                                                       III          T.sub.3  = .13680B                                                                          1.65<ND.sub.3 <1.67                                                                    √.sub.3  ≅ 50               R.sub.6  =- 1.50260B                                                                           S.sub.4  = .6660B                                            R.sub.7  =+ 28.4788B                                                                    T.sub.4  = .08208B                                                                          1.77<ND.sub.4 <1.79                                                                    √.sub.4  ≅ 26            IV R.sub.8  =  .80405B                                                                     T.sub.5  = .19152B                                                                          1.56<ND.sub.5 < 1.58                                                                   √.sub.5  ≅ 56               R.sub.9  =- 1.2324B                                                        __________________________________________________________________________     Wherein B is 16 to 21mm.?                                                

A specific embodiment of the present invention is an objective wherein Bis equal to 18.275mm and has the values set forth in Table II whereinradii, thicknesses and spacings are in millimeters.

                                      TABLE II                                    __________________________________________________________________________                              Index of                                                                               Abbe                                       Lens                                                                             Radius (R)                                                                             Thickness (T)                                                                        Spacing (S)                                                                          Refraction (ND)                                                                       No. (√)                              __________________________________________________________________________                       S.sub.1  = 4.940                                              R.sub.1  =-  5.200                                                         I           T.sub.1  = 1.500                                                                            ND.sub.1  = 1.54062                                                                   √.sub.1  = 47.14                        R.sub.2  =  71.456                                                                            S.sub.2  = 1.622                                              R.sub.3  =-  59.053                                                        II          T.sub.2  = 2.500                                                                            ND.sub.2  = 1.65833                                                                   √.sub.2  = 50.86                        R.sub.4  =-  8.540                                                                            S.sub.3  = 2.696                                              R.sub.5  =  43.468                                                         III         T.sub.3  = 2.500                                                                            ND.sub.3  = 1.65833                                                                   √.sub.3  = 50.86                        R.sub.6  =- 27.460                                                                            S.sub.4  = 12.171                                             R.sub.7  =  520.450                                                                    T.sub.4  = 1.500                                                                            ND.sub.4  = 1.78444                                                                   √.sub.4  = 26.07                     IV R.sub.8  =  14.694                                                                     T.sub.5  = 3.500                                                                            ND.sub.5  = 1.56874                                                                   √.sub.5  = 56.09                        R.sub.9   =- 22.522                                                        __________________________________________________________________________

The values of the objectives, as stated herein, are independent ofnormal manufacturing tolerances and may be modified with the scope ofthe invention as defined in claims.

What is claimed is:
 1. A microscope objective having a numericalaperture of 0.25 which consists of, in alignment along an optical axis,a biconcave negative singlet I, a positive meniscus singlet II concaveto the object side, a biconvex positive singlet III and a biconvexpositive doublet IV consisting of a negative meniscus and a positivebiconvex lens
 2. The microscope objective of claim 1 having thefollowing optical parameters

    __________________________________________________________________________                               Index of Abbe                                      Lens                                                                             Radius (R)                                                                              Thickness (T)                                                                        Spacing (S)                                                                          Refraction (ND)                                                                        No. (√)                            __________________________________________________________________________                        S.sub.1  = .27032B                                           R.sub.1  =-  .28454B                                                       I            T.sub.1  = .08208B                                                                          1.53<ND.sub.1 <1.55                                                                    √.sub.1  ≅ 47               R.sub.2  =  3.91004B                                                                           S.sub.2  = .08876B                                           R.sub.3  =- 3.23135B                                                       II           T.sub.2  = .13680B                                                                          1.65<ND.sub.2 <1.67                                                                    √.sub.2  ≅ 50               R.sub.4  =-  .46730B                                                                           S.sub.3  = .14752B                                           R.sub.5  =  2.37855B                                                       III          T.sub.  = .13680B                                                                           1.65<ND.sub.3 <1.67                                                                    √.sub.3  ≅ 50               R.sub.6  =- 1.50260B                                                                           S.sub.4  = .6660B -                                                                  R.sub.7  =+ 28.4788B                                            T.sub.4  = .08208B                                                                          1.77<ND.sub.4 <1.79                                                                    √.sub.4  ≅ 26            IV R.sub.8  =   .80405B                                                                    T.sub.5  = .19152B                                                                          1.56<ND< 1.58                                                                          √.sub.5  ≅ 56               R.sub.9  =- 1.2324B                                                        __________________________________________________________________________     wherein B is 16 to 21mm.                                                 


3. The microscope objective of claim 2 wherein B is equal to 18.275mm,ND₁ =1.54062; ND₂ =1.65833; ND₃ =1.65833; ND₄ =1.78444 and ND₅ =1.56874and √₁ =47.14; √₂ =50.86; √₃ =50.86; √₄ =26.07 and √₅ =56.09.